In the field of FA (Factory Automation), control in which various kinds of devices take charge of parts of a work process is performed. In order to cooperatively operate various controllers, a remote I/O, and a production device, which are used in work in a given region such as a factory facility, an industrial network system also called a field network is constructed to connect these devices.
In many industrial network systems, production facilities are controlled while various slave devices that perform data collection and control of the production facilities installed in a factory and a master device that intensively controls a plurality of slave devices are connected through a communication bus.
The network including the master device and the slave devices may have various topologies such as an in-line shape, a ring shape, a tree shape and a star shape according to cooperation between the devices and a situation of wiring. For example, in the in-line topology, all the slave devices are included in one transmission path with the master device as a starting point. Assuming that the master device is located on an upstream side, an information signal transmitted from the upstream side passes sequentially through the slave devices connected in series to the transmission path, and the information signal returns to the master device after reaching the slave device located at a downstream end. In the ring-shape topology, the master device includes a port on the side on which the information signal is transmitted and a port on the side on which the information signal is received. The transmitted information signal is returned from the port on the reception side after passing continuously through the slave devices.
Thus, in the in-line topology or the ring-shape topology, the information signal passes through the one transmission path with no branch.
On the other hand, in the tree-shape or star-shape topology, the transmission path from the master device is branched. A hub device is disposed as a network device in a branching place. The hub device includes one port connected on the upstream side and a plurality of ports connected to the downstream slave devices. The hub device can be regarded as a kind of the slave device that takes care of the transmission path control of the network.
A technology called industrial Ethernet (registered trademark) to which an Ethernet technology is applied is being developed as an example of the industrial network aimed at the FA field. Industrial Ethernet is also called technical Ethernet or real-time Ethernet, and is the network system in which the Ethernet technology and device are introduced to an FA system in various layers. Various associations define and disclose an open standard as industrial Ethernet, and EtherCAT (registered trademark, Ethernet for Control Automation Technology) driven forward by ETG (EtherCAT Technology Group) is one of the open standards.
In an EtherCAT standard, the in-line connection and the branch in which the hub device is used can be combined, and various topologies are supported. In EtherCAT, the information signal (frame) is not transmitted from the master device to a specific destination, but the identical information signal goes around all the slave devices. Because the information signal includes control data of each slave device during control operation, the slave device reads a target portion of itself from the information signal and rewrites a content of the information signal as needed basis during the passage of the information signal through the slave device. Accordingly, because the information signal reaches the downstream end without remaining in one place of the network, the high-speed communication can be implemented without collision of data.
As described above, the information signal in EtherCAT moves in the network while following what is called a unicursal path. The characteristic is unchanged even in the topology including the branching place. That is, when the information signal transmitted from the master device reaches the hub device that is of the branching place, the information signal is transmitted to the slave device connected to one of the ports of the hub device. In the case where another slave device exists on the downstream side of the slave device, the information signal is sequentially delivered in the in-line manner, and the information signal is returned after reaching the downstream end. Then the information signal is transmitted to the slave device connected to another port of the hub device.
In designing the network system pursuant to the EtherCAT standard, as described above, it is necessary to make design with a consciousness of a connection sequence between the slave devices or which port of the hub device is to be connected to the slave device. A design support system is provided in order to facilitate the design work, when a user who does not have expert knowledge or an experience unlike an SE performs system design or assembly of a real machine. The design support system has a form like a management device connected to the master device. For example, the management device is a personal computer on which a setting tool that is of a setting information generating application is installed.
Patent Document 1 describes a communication system in which the master device and the slave device are connected to each other on a double conductive wire structure.
Patent Document 1: International Patent Publication No. 2010-510741